[Bug binutils/2467] "ar q" gives quadratic memory use

[dcoutts at gentoo dot org]

------- Additional Comments From dcoutts at gentoo dot org  2006-03-17 02:57 
-------
Adding some instrumantation shows that the spike in memory use occurs within the
function _bfd_compute_and_write_armap() in bfd's archive.c module.

It maps over each object file in the archive and allocates symbol tables for
each one. This is where the linear memory use is comming from. Then when it's
done collecting symbols it writes them out.

Perhaps it'd be possible to change the algorithm so that we only need to keep
the bfd resources for one archive member at a time. Afterall the code already
copies out the information it will need for the final symbol index rather than
leaving it shared with the archive member bfd structures. So as far as I can see
it should be possible to only allocate bfd resources for one member of the
archive at a time rather than allocating bfd resources for every archive member
simultaniously.

The size of the final symbol index is not that big (only a few Mb) so if the
memory use were a small multiple of that size rather that a large multiple (x20)
of the size of the whole archive then the memory savings would be quite 
significant.

[And we wouldn't get complaints from users about the OOM killer kicking in while
they build libHSbase.a ! :-) ]

-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=2467

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